Bearbait has a good idea. Had a 4 inch pvc that takes excess water away from our leach field freeze several years ago. The open end is at a creek some 300 ft from the water heater. Water heater has acme (garden hose) threads on the bottom so ran hose out and put a brass jet nozzle on. Band clamped the first 2 ft of hose to a telescoping paint roller pole and blasted a hole after a tank or two for full flow. May of had 6- 8 ft of blockage dont remember.I had a cleanout some 100 ft away from the blockage that I put some large pellet softner salt in for the rest of the winter and the line stayed open.That water runs to our lower pond and caused no problems.We are colder this year but have a lot more snow so no freeze up to date.